On 8 juin 2014, at 19:20, Garth Holland <steve9571...@hotmail.com> wrote:
> The pipe operator appears in many languages (F#, Haskell, Elixir, Clojure
> (threading macro)). It's an elegant way of chaining method/function calls in
> the presence of additional parameters. The reddit example could be written
> using a pipe operator |>
>
> #('apple' 'peach' 'banana')
> |> groupedBy: #size
> |> select: [:each | each size even]
> |> values
> |> collect: #asCommaString.
The pipe operator is implemented as one of the examples of LanguageBox, a tool
that permits to scope language extensions (it's a part of Helvetia made by
Lucas Renggli).
I once thought that the pipe operator could be useful. But now I notice that
the main (if not the only) recurrent use case I found is chaining queries on
collections.
If you have another recurrent use case (that is not purely idiomatic :) )
please let me know.
So yes, using the pipe operator make the snippet more readable but still has
much inefficient: at each step a new collection is created just to be trashed
afterward.
Here it's not a problem but not all collections only have 3 elements ;).
For me it's a sign that the collection libraries lack a simple abstraction:
composable filters (that is, iterators) to make complex queries.
We could have collections answering #query that would responds a QueryBuilder
object that would understand common enumeration methods, for example:
#('apple' 'peach' 'banana') query
groupedBy: #size;
select: [:each | each size even];
values;
collect: #asCommaString.
This would return a CollectFilter on a ValuesFilter on a SelectFilter on a
GroupedByFilter on the input collection.
The QueryBuilder could then answer a message like #endQuery to compute and
return the values obtained by the lastly created filter (embedded in a
collection that conforms to the input collection's #species).
Since it's just a composition of filter objects over the input collection, no
useless intermediate collection is created: better performances & less stress
on the GC.
Of course this idea is acceptable only if they are no other use cases where the
pipe operator is a must.
>
> /Garth
>
>
>
>
> --
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